Microbial hydroxylations of β-carboline derivatives

Ethyl β-carboline-3-carboxylate (1a) and its 4-alkyl derivatives (1b–d) are hydroxylated by Sporotrichum sulfurescens at C-6 and C-8 of the aromatic nucleus; side chain hydroxylation of (1c) and (1d) occurs with Streptomyces lavendulae and Streptomyces griseus.